Abstract： Objective To understand molecular characteristics of Japanese encephalitis virus ( JEV ) isolated from the major Japanese encephalitis epidemic areas in Sichuan Province,and to provide the foundation for JEV prevention.Methods 13 JEV strains were isolated from mosquitoes in Sichuan during 2007-2010,E genes and preM genes were sequenced and phylogenetic analyses were performed using MEGA5 molecular software.Results Phylogeoetic analysis indicated that all 13 JEV strains from Sichuan belonged to genotype Ⅰ,homologies at nucleotide level and deduced amino acid level in PreM gene were 97％-100％ and 98.7％-100％,and 97.8％-99.9％ and 99.6％-100％ in E gene,respectively.Homologies at nucleotide level and deduced amino acid level in PreM gene between 13 JEV strains and JEV isolated in 2004 in Sichuan were 96.2％-99.1％ and 97.5％-98.7％,and were 97.7％-99.6％ and 98.6％-100％ in E gene,respectively.By comparison with vaacine strains P3 and SA14-14-2,homologies at nucleotide level and deduced amino acid level were 84.1％-85.8％ and 93.7％-96.2％ in PreM gene,and were 87.6％-88.3％ and 97％-97.8％ in E gene,respectively.The neurovirulence-related 8 amino acid sites encode by E gene remained unchanged in 13 JEV strains.Conclusion JEV with genotype Ⅰ predominated in Sichuan,nucleotide sequences and deduced amino acid sequences in PreM gene and E gene were highly conserved,key neurovirulence-rerlated sites remained unchanged.It suggested currently used vaccine is still capable of preventing JEV infection.